600 research outputs found
SIMP Spectroscopy
We study the interactions between strongly interacting massive particle dark
matter and the Standard Model via a massive vector boson that is kinetically
mixed with the hypercharge gauge boson. The relic abundance is set by 3-to-2
self-interactions of the dark matter, while the interactions with the vector
mediator enable kinetic equilibrium between the dark and visible sectors. We
show that a wide range of parameters is phenomenologically viable and can be
probed in various ways. Astrophysical and cosmological constraints are evaded
due to the p-wave nature of dark matter annihilation into visible particles,
while direct detection methods using electron recoils can be sensitive to parts
of the parameter space. In addition, we propose performing spectroscopy of the
strongly coupled dark sector at e+e- colliders, where the energy of a
mono-photon can track the resonance structure of the dark sector.
Alternatively, some resonances may decay back into Standard Model leptons or
jets, realizing `hidden valley' phenomenology at the LHC and ILC in a concrete
fashion.Comment: 35 pages, 8 figures; v2: matches published version; v3: fixed typos
in Eqs. (4.15), (6.7) and (6.9), results unchange
Implications of Higgs Searches on the Four Generation Standard Model
Within the four generation Standard Model, the Higgs couplings to gluons and
to photons deviate in a significant way from the predictions of the three
generation Standard Model. As a consequence, large departures in several Higgs
production and decay channels are expected. Recent Higgs search results,
presented by ATLAS, CMS and CDF, hint on the existence of a Higgs boson with a
mass around 125 GeV. Using these results and assuming such a Higgs boson, we
derive exclusion limits on the four generation Standard Model. For m_H = 125
GeV, the model is excluded at 99.9% confidence level. For 124 GeV <= m_H <= 127
GeV, an exclusion limit above 95% confidence level is found.Comment: 4 pages, 2 figures; v2: updated LHC results, refined sca
Extracting the Dark Matter Mass from Single Stage Cascade Decays at the LHC
We explore a variant on the MT2 kinematic variable which enables dark matter
mass measurements for simple, one stage, cascade decays. This will prove useful
for constraining a subset of supersymmetric processes, or a class of
leptophilic dark matter models at the LHC. We investigate the statistical reach
of these measurements and discuss which sources of error have the largest
effects. For example, we find that using only single stage cascade decays with
initial state radiation, a measurement of a 150 GeV dark matter candidate can
be made to O(10%) for a parent mass of 300 GeV with a production cross section
of 100 fb and 100 fb^(-1) of integrated luminosity.Comment: 23 Pages, 14 Figures, 2 Appendice
Models of Dynamical R-Parity Violation
The presence of R-parity violating interactions may relieve the tension
between existing LHC constraints and natural supersymmetry. In this paper we
lay down the theoretical framework and explore models of dynamical R-parity
violation in which the breaking of R-parity is communicated to the visible
sector by heavy messenger fields. We find that R-parity violation is often
dominated by non-holomorphic operators that have so far been largely ignored,
and might require a modification of the existing searches at the LHC. The
dynamical origin implies that the effects of such operators are suppressed by
the ratio of either the light fermion masses or the supersymmetry breaking
scale to the mediation scale, thereby providing a natural explanation for the
smallness of R-parity violation. We consider various scenarios, classified by
whether R-parity violation, flavor breaking and/or supersymmetry breaking are
mediated by the same messenger fields. The most compact case, corresponding to
a deformation of the so called flavor mediation scenario, allows for the
mediation of supersymmetry breaking, R-parity breaking, and flavor symmetry
breaking in a unified manner.Comment: v2: references adde
Light Neutralinos with Large Scattering Cross Sections in the Minimal Supersymmetric Standard Model
Motivated by recent data from CoGeNT and the DAMA annual modulation signal,
we discuss collider constraints on MSSM neutralino dark matter with mass in the
5-15 GeV range. Such an LSP would be a Bino with a small Higgsino admixture.
Maximization of the DM-nucleon scattering cross section for such a WIMP
requires a light Higgs boson with tan beta enhanced couplings. Limits on the
invisible width of the Z boson, when combined with Tevatron constraints on
Higgs bosons at large tan beta, and the rare decay
constrain cross sections to be below . This indicates a slight local Dark Matter over-density would be
necessary to explain the CoGeNT excess. This scenario also requires a light
charged Higgs boson, which can give substantial contributions to rare decays
such as and .Comment: 5 pages, 3 figures. v2: refs updated, minor typos corrected, new
discussion on B->D\tau\nu, journal versio
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